The invention relates to kneader mixers, and more particularly to kneader-mixers for the mechanical and thermal treatment of products in a liquid, pasty and/or pulverulent state.
One type of such kneader-mixer, described in Swiss Pat. No. 583061, contains a heatable cylindrical casing and a stirrer shaft coaxially rotating therein with disk elements which are rectangularly mounted on the shaft and which cooperate with hook-like kneading counterelements are arranged within longitudinal sectional planes passing through the casing axis. In this arrangement, the open vicinity of the hook-like kneading counterelements. Practice has shown that in the case of certain structurally viscous products, e.g. cellulose derivatives or alkaline alkoxides, material builds up on the counterhooks. This can lead to the formation of toroidal structures which greatly constrict a large part of the machine required for conveying and discharging the product and the gases which may form. Another disadvantage of this construction and arrangement is that the scraping edges of the hook-like kneading counterelements are directly and simultaneously stressed vertically thereby requiring a high force expenditure leading to rapid wear of the scraping edges and reduced efficiency in the removal of crusts from the heated surfaces.
The object of the present invention is to overcome or substantially reduce the above mentioned disadvantages inherent in such known kneader-mixer constructions and arrangements.